Question

which reagent is responsible for staining gram - positive bacteria purple?
a) safranin
b) crystal violet
c) iodine
d) 95% ethyl alcohol

Explanation:

In Gram - staining, crystal violet is the primary stain. It binds to the thick peptidoglycan layer in Gram - positive bacteria. Safranin is the counter - stain (used to stain Gram - negative bacteria pink/red after decolorization). Iodine is a mordant that fixes the crystal violet stain. 95% ethyl alcohol is the decolorizing agent.

Answer:

B. Crystal violet